Medium Ring Ethers by Ring Expansion−Ring Contraction:  Synthesis of Lauthisan

Abstract

[reaction: see text] A new general method for the construction of medium ring ethers has been developed. This involves the ring expansion of halo-O,S-acetals followed by a Ramburg-Bäcklund ring contraction reaction with concomitant extrusion of the sulfur atom. This methodology has been utilized for the synthesis of cis- and trans-lauthisan.

Z-Group Ketone Chain Transfer Agents for RAFT Polymer Nanoparticle Modification via Hydrazone Conjugation

“…Synthesis of Benzyl 2-(2-Methyl-1,3-dioxolan-2-yl)ethyltrithiocarbonate (1a). S-Acetyl-4-mercapto-2-butanone (1.46 g, 0.01 mol) is commercially available but was readily prepared from Michael addition of CH 3 COSK to methyl vinyl ketone 20 and converted to the acetal by reaction with ethylene glycol (2.48 g, 0.04 mol) and D-tartrate (0.05 g) in refluxing THF for 12 h using a Dean−Stark apparatus. The reaction mixture was concentrated under reduced pressure, dissolved in 80 mL of CH 2 Cl 2 , washed with saturated aqueous NaHCO 3 , dried over anhydrous Na 2 SO 4 , and concentrated under reduced pressure to give the desired acetal 21 in quantitative yield.…”

Electrophilic Functionalization of Non-Activated Olefins Catalyzed by Lewis Superacids

“…Thiols are known to be among the most powerful sulfur compounds from the point of view of their organoleptic properties. 187,188 Several examples report the conjugate addition of thioacetic acid to conjugated olefins in a Michael-type reaction in basic media, 189 and the use of Montmorillonite K10 has also been reported for the addition of thiobenzoic acid to conjugated olefins. 190 Besides the regioselectivity and the high yields obtained under mild conditions, an interesting illustration of the scope of the In(OTf) 3 -catalyzed thiol and thioacid addition method to olefins lies in the possibility to obtain new sulfurated camphene derivatives without the classical rearrangement to isobornyl compounds.…”